Circinus X-1, the Lord of the Rings

The astronomers used a method that exploits the geometry of the echoes light products following an outburst of a neutron star in a binary system. The results of this study, reported in the Astrophysical Journal, allow us to experiment with a technique that could be used to estimate distances sources X. Now astronomers know that Circinus X-1, one of the most bizarre objects in our galaxy, is 30,700 light years from Earth.


Credit: Univ. of Wisconsin-Madison/S.Heinz et al.

An outburst, that is a massive emission of high-energy visible in the form of X-rays, which originated towards the end of 2013 from a neutron star, located in the heart of one of the strangest supernovae in our galaxy, it has produced the echoes bright they are created when X-rays are bounced on the dust clouds of interstellar space. With great surprise, the astronomers were able to take advantage of this event to obtain a sort of “cosmic ruler” that allowed to estimate the distance to which is Circinus X-1 (Cir X-1). The results of this study are reported in the Astrophysical Journal.
Located in the galactic plane, Circinus X-1 is a “monster of the sky”, a sort of “skin glow” that is part of a binary star system. The system consists of a nebula and a neutron star, the collapsed core it, incredibly dense, of a star that exploded about 2500 years that still remains tied to the embrace of its orbital companion star. The star system is called binary X because as the matter of the companion star falls, spiraling toward the neutron star it is heated to very high temperatures by emitting X-rays as “Towards the end of 2013, the neutron star fathered a huge outburst that lasted about two months, becoming one of the brightest X-ray sources in the sky, “said Sebastian Heinz of the University of Wisconsin-Madison. “Then it is off.”
The subtle variations of X-radiation from the binary system were monitored by a detector located on board the International Space Station. The research team, led by Heinz, planned in a timely manner a series of successive observations, thanks to the space observatory Chandra and XMM-Newton satellite, which led to the discovery of four rings brilliant X-ray, similar to the ripples present in a “pool cosmic”, surrounding the neutron star located in the heart of Circinus X-1. The rings X are the echoes generated by light dell’outburst Circinus X-1. “Each of the four rings,” he says Heinz, “is a dense cloud of dust interposed along the line of sight. When X-rays encounter the dust particles of interstellar space they are deflected. And if these dust clouds are very dense, they can spread a considerable fraction of X-rays from their original direction, causing them to take a triangular path. ”


Credit: NASA/Chandra X-ray Observatory

According to the authors, this phenomenon could provide astronomers a way to take advantage of the geometry of the light rings and the time lag between the X-rays scattered and not in order to calculate the distance to where the star system, a measure that has not been possible before because the supernova is hidden by dust that are distributed in the galactic plane. “We can use the geometry of the rings of light and the time delay to make a kind of tomography X” continues Heinz. “Because X-rays have traveled following a triangular path rather than in a straight line, they take longer before you get there.”
Thus, by combining measurements made by researchers with the observations of the clouds of dust made the telescope Mopra located in Australia, the team was able to determine which dust clouds are actually responsible for each of the four light echoes. “By means of this identification technique, we can accurately determine, and for the first time, the distance at which the source is located. In astronomy, distance measurements are complicated, especially for items like Circinus X-1 which is hidden in the plane of the Milky Way with a thick layer of dust, making it impossible to perform observations with optical telescopes. In this case, we used differently the presence of dust to explore a new approach that allows us to estimate the distances of X-ray sources, “concludes Heinz. Through this work, astronomers now know that Circinus X-1, one of the most bizarre objects in our galaxy, is 30,700 years light from Earth.

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